Available at: http://digitalcommons.calpoly.edu/theses/152
Date of Award
MS in Engineering - Biomedical Engineering
Biomedical and General Engineering
Kristen O'Halloran Cardinal, PhD
PREPARATION AND CHARACTERIZATION OF ELECTROSPUN POLY(D,L-LACTIDE-CO-GLYCOLIDE) SCAFFFOLDS FOR VASCULAR TISSUE ENGINEERING AND THE ADVANCEMENT OF AN IN VITRO BLOOD VESSEL MIMIC
Tiffany Richelle Peña
Currently, an estimated 1 in every 3 adult Americans are affected by one or more cardiovascular complications. The most common complication is coronary artery disease, specifically atherosclerosis. Outcomes of balloon angioplasty treatments have been significantly improved with the addition of drug eluting stents to the process. Although both bare metal and drug eluting stents have greatly increased the effectiveness of angioplasty and decreased the occurrence of restenosis, several complications still exist. For this reason, the stent industry is continually advancing toward better stent and drug-eluting designs, deployment methods, and adjuvant drug therapies, necessitating fast, reliable pre-clinical test methods. Recently, advancements in tissue engineering have led to the development of an in vitro blood vessel mimic (BVM) and the feasibility of evaluating cellular response to intravascular device implantation has been demonstrated. There are several physiological and scalability limitations of the current BVM model that must be addressed before effective use of the model can be initiated. The limiting aspect addressed in this thesis is the use of expanded poly(tetrafluorethylene) [ePTFE] scaffolding for the development of the BVM. There are several disadvantages and limitations to ePTFE including high cost and non-native mechanical properties. The ability to produce and tailor scaffolds in-house would greatly impact the scalability, cost effectiveness, and control over scaffold properties for BVM optimization. Also, in-house fabrication will open up further avenues of research into optimum scaffold design for better cellular responses when cultured in vitro.
Electrospinning is a relatively simple and economical method of creating tissue engineering constructs with micro-architecture similar to the native extracellular matrix. Based on the clinical problem and the potential for the BVM, the aim of this thesis is to employ electrospinning for the development of poly(D,L-lactide-co-glycolide) [PLGA] vascular scaffolds as a replacement to ePTFE for the BVM. After primary literature review, PLGA was determined an advantageous polymer for tissue engineering vascular scaffolds and electrospinning based on evidence of adequate endothelial cell attachment, mechanical properties similar to the native vessels, controlled degradation, and good biocompatibility. The first phase of this thesis was to develop an acceptable protocol for the fabrication of electrospun PLGA scaffolds by varying solution concentration, flow rate and applied voltage. Electrospun solutions of 15 wt% PLGA in CHCl3 resulted in continuous un-beaded fibers of 5-6 microns and tensile properties (3-5 MPa) similar to the native vessel. The optimum protocol for electrospinning 15 wt% PLGA incorporated a flow rate of 5.5 ml/hr and an applied voltage of 12,000 V. In the second phase of this thesis, final protocol PLGA scaffolds were cultured in vitro with human umbilical vein endothelial cells (HUVECs) up to 6 days. Fluorescent microscopy and SEM analysis suggest the porous nature of the scaffolds was conducive to sub-luminal cellular penetration. Although results were not optimal for developing an endothelium for the ideal BVM design, the potential of using electrospinning for in-house production of scaffolds for tissue engineering was established. Further optimization of the electrospinning protocol to develop nano-sized structural features could enhance the ability to form an intimal lining of endothelial cells for the next generation BVM design.